From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B534C433E0 for ; Mon, 4 Jan 2021 13:35:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D67012075B for ; Mon, 4 Jan 2021 13:35:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726811AbhADNfh (ORCPT ); Mon, 4 Jan 2021 08:35:37 -0500 Received: from mga14.intel.com ([192.55.52.115]:26556 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726308AbhADNfh (ORCPT ); Mon, 4 Jan 2021 08:35:37 -0500 IronPort-SDR: UmpDFPRV9gY0Ms4kQusiDChF5dX9MIP10XhXvYMC1zZ01lQOyuYvlLPUqv7QpmhrT8Z0YFdHwd n0TlVMR4ECWg== X-IronPort-AV: E=McAfee;i="6000,8403,9853"; a="176172253" X-IronPort-AV: E=Sophos;i="5.78,474,1599548400"; d="scan'208";a="176172253" Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 04 Jan 2021 05:34:48 -0800 IronPort-SDR: ZC72G4Xg7XmdPpH9pGGCkSQvY+CVk1z4afxu9vUOCrMjsQyvdfXczPpgZKpjXl9QTd98/PDGZ5 2IxKMdHKswyA== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.78,474,1599548400"; d="scan'208";a="349942515" Received: from shbuild999.sh.intel.com (HELO localhost) ([10.239.147.98]) by fmsmga008.fm.intel.com with ESMTP; 04 Jan 2021 05:34:45 -0800 Date: Mon, 4 Jan 2021 21:34:45 +0800 From: Feng Tang To: Michal Hocko Cc: Andrew Morton , Johannes Weiner , Vladimir Davydov , linux-mm@kvack.org, linux-kernel@vger.kernel.org, andi.kleen@intel.com, tim.c.chen@intel.com, dave.hansen@intel.com, ying.huang@intel.com, Roman Gushchin Subject: Re: [PATCH 1/2] mm: page_counter: relayout structure to reduce false sharing Message-ID: <20210104133445.GA101866@shbuild999.sh.intel.com> References: <1609252514-27795-1-git-send-email-feng.tang@intel.com> <20210104130357.GF13207@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210104130357.GF13207@dhcp22.suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Michal, On Mon, Jan 04, 2021 at 02:03:57PM +0100, Michal Hocko wrote: > On Tue 29-12-20 22:35:13, Feng Tang wrote: > > When checking a memory cgroup related performance regression [1], > > from the perf c2c profiling data, we found high false sharing for > > accessing 'usage' and 'parent'. > > > > On 64 bit system, the 'usage' and 'parent' are close to each other, > > and easy to be in one cacheline (for cacheline size == 64+ B). 'usage' > > is usally written, while 'parent' is usually read as the cgroup's > > hierarchical counting nature. > > > > So move the 'parent' to the end of the structure to make sure they > > are in different cache lines. > > Yes, parent is write-once field so having it away from other heavy RW > fields makes sense to me. > > > Following are some performance data with the patch, against > > v5.11-rc1, on several generations of Xeon platforms. Most of the > > results are improvements, with only one malloc case on one platform > > shows a -4.0% regression. Each category below has several subcases > > run on different platform, and only the worst and best scores are > > listed: > > > > fio: +1.8% ~ +8.3% > > will-it-scale/malloc1: -4.0% ~ +8.9% > > will-it-scale/page_fault1: no change > > will-it-scale/page_fault2: +2.4% ~ +20.2% > > What is the second number? Std? For each case like 'page_fault2', I run several subcases on different generations of Xeon, and only listed the lowest (first number) and highest (second number) scores. There are 5 runs and the result are: +3.6%, +2.4%, +10.4%, +20.2%, +4.7%, and +2.4% and +20.2% are listed. Thanks, Feng